1. Field of the Invention
The present invention relates to an apparatus for optically reproducing data recorded on a recording medium in the form of marks.
2. Description of the Related Art
With recent development of the information-oriented society, the amount of data to be processed increases more and more, and there is a strong demand for a system capable of recording/reproducing a great deal of data. To meet the demand, various optical data processing systems capable of recording/reproducing data at a high density have been proposed. According to these systems, data is recorded on a recording medium, after it was coded into optically detectable physical marks. These marks are optically detected, thereby reproducing data. The physical marks include recesses (pits), projections, and openings formed on a recording medium. In this case, analog data is recorded in the form of marks having various lengths in the track direction in accordance with the analog data. Digital data is recorded in the form of, for example, a series of marks arranged along the track on the medium. An example of this recording medium is a compact disc which has been widely used. Although the compact disc is most popular in the field of music software, it is also used as a CD-ROM or a computer memory. The capacity of the CD-ROM is 1,000 times or more greater than that of a 5.25" floppy disc which is conventionally used in personal computers.
The above-stated optical data processing system can meet the present demand to some extent; however, there is a demand for a new, improved data processing system capable of recording data at a higher density. To meet the demand, new processing systems have been studied and developed extensively.